Screw-cutting die



NITED STATES PATENT @rrrca FRANCIS I-. MAULE, OF PHILADELPHIA,PENNSYLVANIA.

SCREW-CUTTING DiE.

SPECIPICATION'I'Orming part of Letters Patent No. 38 aated April 1988-Application filed December '7. 1887. Serial No. 257,904. (No model.)

To CLZZ whom it may concern.-

Be it known that I, FRANCIS I. MAULE, a citizen of the United States,and a resident of Philadelphia, Pennsylvania, have invented certainImprovements in Screw-Cutting Dies, of which the following is aspecification.

The object of my invention is to so construct a screw-cutting die thatthe cost of manufacture will be reduced to a minimum, the cutting-bitsrigidly supported in the stock, and provision afforded for the readyremoval and replacing of any one of said bits. This obj ectI attain inthe manner which I will now proceed to describe, reference being had tothe accom- Q panying drawings, in which Figure 1 is a perspective viewof a screwcutting die constructed in accordance with my invention. Fig.2 is a sectional plan view of the same; and Fig. 3 is a transversesection on the line 1 2, Fig. 2.

The stock of the die consists of a block, A, preferably of malleableiron or cast-steel, and of the cruciform shape shown in the drawings,for the purpose of reducing its weight, although the block may, ifdesired, be rectangular, as shown by dotted lines in Fig. 2. In thisblock are formed radial recesses for the reception of the cutting'bitsa, which fit snugly in these recesses, the back of each bit having arigid bearing against the base of the slot and the sides of the bitbearing against the sides of the slot. The bits are retained in theslots by means of transverse pins b, driven through openings in the bitsand in the arms of the block, or across the corners of the same if theblock is of rectangular form. These pins, however, are not intended toresist the strain upon the cutting-bits in the operation of the tool,but are simply for holding the bits in place, reliance being placed uponthe rigid bearing of the bits against the sides and bases of the slotsin the block to withstand anystrain to which said bits may be subjectedin the operation of the tool. The slots for the recep:

tion of the bits extend through from face to face of the block A, andare of uniform size and shape throughout, so that they may be readilymade true by means of a drifting-tool passed through from one face ofthe block to the other.

Although the cutting-bits are firmly retained in the block, any one ofthe bits can be readily removed by driving out the transverseretaining-pin, and a 'new bit can then be inserted and as readilysecured in place by the reinsertion of the pin.

It will be seen that my improved screw-cutting die comprises but fewparts, and that no expensive fitting is demanded in the construction ofthe same, so that the tool can be manufactured very cheaply, thischeapness of manufacture resulting without any impairment of theefficiency of the tool.

I claim as my invention- 1. The combination of the block having slotsextending completely through the same from face to face, and havingopposite sides parallel from face to face of the block, withcutting-bits fitting snugly in said slots, and transverse retaining-pinspassing through openings in the block and bits, all substantially asspecified.

2. The combination of the block having a central opening, and slotsextending outward therefrom, with cutting-bits fitting snugly in saidslots and bearing at their outer ends against the bases of the slots,and transverse pins passing through openings in the [block and bits andserving to cause said bits to bear firmly against the outer bearings inthe block, all substantially as specified.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

FRANCIS I. MAULE.

\Vitnesses:

WILLIAM D. CONNER, HARRY SM TH.

